Device to indicate operating state of a linear actuation valve

Abstract: A device (3) for indicating the operating state of a linear actuation valve (5) comprises a mounting plate (9) having a rectilinear slot (11) therein for slidably receiving a perpendicularly extending follower stem (6) fixed to a follower nut (4). The nut (4) is threaded to the exterior of a sleeve (7) which is mounted for conjoint rotation with the hub of a hand wheel (2) of the linear actuation valve. Engagement of the follower stem (6) with the slot (9) prevents rotation of the nut (4) and provokes it to moveaxially relative to the sleeve (7). The mounting plate (9) also includes means for fixing sensors (15) and (16) to the plate for detecting arrival of the follower stem (6) moving along the slotin either of two positions to be detected.

Description: This invention relates to a device for indicating the operating state of a linear actuation valve, to show e.g. whether the valve is fully open or fully shut. This device may be fitted on the valve, for example between the valve wheel and the bonnet of the linear actuation valve, and is provided with sensors which will indicate whether the valve is fully open or fully shut. Owing to the ever-increasing growth of remote control systems meant to operate some kind of process, the need has been felt for various kinds of device to indicate fundamental parameters for different sorts of equipment. As regards manually-operated linear actuation shut-off or block valves, which valves are widely used in the flow of liquids, it is becoming important that the operating state of the valve - whether open or shut - be known at a remote location. Various ways of dealing with this problem have been put forward. EP-A-0369918 teaches the use of two coils concentrically fitted to the valve shutter, the first coil inducing a voltage in the second coil, in a direct relationship to the position of the valve shutter so as to enable the state of the valve to be correctly indicated. This arrangement works well but one of its chief drawbacks is that because there are a lot of mechanical and electrical parts, the manufacturing cost is high, and the large number of electrical parts makes it more likely to break down. US-A-4967792 brings in the use of small magnetized parts fixed to the valve stem, together with a device fitted between the bonnet and the valve wheel and able to detect the magnetic field generated about such small parts when they pass close to sensors lying within the device. A signal is thereby generated to indicate the operating state of the valve, that is, whether it is open or shut. This arrangement works well but is hampered by the fact that the valve stem has to be drilled, thereby diminishing the valve stem cross-sectional area which may affect strength of the stem at such drilled points. US-A-2,407,944 discloses an indicator device comprising an externally threaded sleeve (7) to be connected to the handwheel (9) of a "non-rising stem" valve to surround the valve shaft (stem) for rotation synchronously with the handwheel, and a follower nut (12) screwed onto the sleeve and having a follower stem (13) extending perpendicularly to the axis of rotation of the threaded sleeve and engaging with a rectilinear slot (16) on a plate (17) to prevent rotation of the nut as it moves along the axis of the valve shaft or stem during rotation of the handwheel. In contrast to this prior art, the present invention enables the operating state of a linear actuation valve to be easily indicated without having to make great changes to any of the original parts of the valve. The object of the invention is to provide a device fitted between the bonnet and the control wheel of a linear actuation valve so that the operating state, of said valve, i.e. whether it is open or shut, may be ascertained. The device is characterised by the features of claim 1. Other objects and advantages of the invention will be more readily perceived from the following detailed description given, merely by way of example, with reference to the accompanying drawings, in which: FIGURE 1 is a front view of a linear actuation valve with the device of this invention for indicating the valve operating state; FIGURE 2 is a side view of the linear actuation valve with the device of this invention; FIGURE 3 is a side view, as a detail of Figure 2, showing details of the threaded sleeve and follower; FIGURE 4 is a front view of the front plate of the device of this invention; FIGURE 5 is a front view of the threaded sleeve; the right hand side of the drawing showing a section and the left hand side an elevational view; and FIGURES 6a and 6b are a front view and a side view, respectively of the follower and the follower stem. The ever growing move towards automation within industry in general has brought about the rise of technologies to deal with the various problems that emerge. As regards the plants for processing of fluids, a great number of devices has been developed to control and supervise such processes, especially to supervise the progress of the process so as to centralise information at one single spot for enabling work to be done more efficiently. For such tasks to be properly carried out much information on supervision and control parameters for processes is collected at several points and directed to an operation, supervision, and control centre. A basic kind of information needed for such plants to operate properly is the operating state of shut-off or block valves, i.e. whether they are open or shut. This sort of information can be easily obtained from valves that have some kind of operating mechanism, whether they are control valves or just power operated block valves. However manually-operated block valves require some sort of device adapted to ensure that their operating state can be sensed remotely. This invention is meant to offer an easy and cheap answer for such problem. Figures 1 and 2 show a linear operating valve 5 with a device 3 fitted on top of it, below the hand wheel 2 that operates the stem 1 of the valve 5. The device 3 for indicating the operating state of the linear actuation valve consists of a front plate 9 shown in greater detail in Figure 4, an externally threaded sleeve 7 shown in greater detail in Figure 5, a part 4 hereinafter referred to as the follower nut, a follower stem 6 attached to the follower nut 4 as can be more easily seen in Figures 6a and 6b, and finally two sensors 15 and 16. The threaded sleeve 7 slips easily over the stem 1 in that the inside diameter of the sleeve is bigger than outside diameter of the stem 1 of the linear actuation valve 5, thus enabling said stem 1 to enter the sleeve with a clearance, without damaging the threads of said stem. The threaded sleeve 7 is fixed to the hub of the hand wheel 2 so as to rotate together with it. In this embodiment the threaded sleeve is fitted to the bushing of the hub of the wheel 2 by means of bolts extending through holes 17 in a collar 8 secured to the sleeve 7. It should be pointed out that other methods may be used for fitting the threaded sleeve 7 to the wheel 2. The follower nut 4 is screwed on to the threaded sleeve 7 and its follower stem 6 has one of its ends fitted to the follower nut 4 so the stem 6 is perpendicular to the sleeve 7. In this embodiment the stem end is threaded so as to be screwed into a threaded hole 14 in the follower nut 4, though other ways of fixing the follower stem 6 to the follower nut 4 may be adopted. Figure 2 is a side view of the linear actuation valve 5 and of the device 3 and shows in greater detail the threaded sleeve 7, the follower nut 4 and the follower stem 6. The front plate 9 of the device 3 has a rectilinear slot 11 in which the follower stem 6 slides, and has two other groups of slots 12 and 13 intended to enable sensors 15 and 16 to be mounted on the plate 9. The front plate 9 has also holes 10 intended for fixing it to the bonnet of a valve such as valve 5 shown. The way in which the device 3 functions to indicate the operating state of linear actuation valve 5 is quite simple. When the hand wheel 2 is turned to open or to shut the linear actuation valve 5, the threaded sleeve 7 turns together with the rotating hand wheel 2 since it is joined to it. The follower nut 4 is driven by the rotating hand wheel 2, as is the follower stem 6 joined to the follower nut 4. However, since the follower stem 6 passes through the slot 11 in the front plate 9, rotation of the assembly of follower nut 4 and follower stem 6 with the rotating hand wheel 2 is prevented by the front plate 9 as the follower stem 6 contacts either edge of the slot 11. Being thus prevented from turning, the follower nut 4 is obliged to travel up or down within the threaded sleeve 7 depending on whichever way the hand wheel 2 is being turned to open or shut the linear actuation valve 5. In following the up or down travel of the follower nut 4, the follower stem 6 approaches sensors 15 or 16 whenever linear actuation valve 5 approaches the fully open or fully shut state. The sensors 15 and 16 are fitted to the front plate 9, by means of the groups of slots 12 and 13. These groups of slots 12 and 13 are so designed as to enable the sensors 15 and 16 to be assembled at spots that are adjustable to be sufficiently close to the follower stem 6 when the latter reaches the limits of its travel, that is its topmost and bottommost limits, as the valve becomes fully open or fully shut. According to the type of sensor employed it may be necessary to fit them in such a way that the follower stem 6 actually touches them. Hence, when the follower stem 6 reaches either end of its travel, the sensor 15 and 16 perceive this, and they send a signal to some remote panel to show that the associated valve has become completely open or shut, as the case may be. The sensors 15 and 16 may be of various kinds, for example mechanically operated ones that operate by contact with the follower stem 6, or electronical sensors where no kind of physical contact is needed, to give but two examples. The linear actuation valve operating indicator device described and claimed herein is quite easy to manufacture, since the materials and parts needed for it are easily found on the market. Besides, the device performs outstandingly, and no specialized staff are needed to install it or to maintain it. The pitch of the threads on the shaft 1 may be the same as that of the external threads on the sleeve 7, but may instead be greater or smaller than it if reduction or magnification of the axial movement of follower stem 6 relative to that of the valve shutter is required.

Claims: A device for indicating the operating state of a linear actuation valve (5) having a rotatable valve shaft (1) carrying a handwheel (2), said device comprising an externally threaded sleeve (7) for arrangement around said shaft (1), means for connecting the sleeve (7) to the handwheel (2) for rotation synchronously therewith, a follower nut (4) screwed on to said externally threaded sleeve (7), and means (6, 9, 11) for preventing rotation of said follower nut (4) during rotation of said threaded sleeve (7), said means (6, 9, 11) comprising a follower stem (6) fixed to said follower nut (4) and extending perpendicularly to the axis of rotation of the sleeve (7), and a plate (9) having a rectilinear slot (11) formed therein, said slot (11) cooperating with said follower stem (6); characterised in that sensors (15, 16) are provided for sensing the position of said follower stem (6) relative to said plate (9) to detect the arrival of the linear actuation valve in one or other of two operating states, for example the valve open state and the valve closed state; and in that the sensors (15, 16) are mounted on said plate (9) by means of slots (12, 13) allowing the positions of the sensors (15, 16) on the plate to be adjusted so that the sensors can sense the longitudinal movement of said follower nut (4) relative to the plate during rotation of said externally threaded sleeve (7). A device according to claim 1, and including a collar (8) on said externally threaded sleeve and having holes (17) for attachment bolts to secure the collar to the hub of a said handwheel (2) of a linear actuation valve whose state is to be sensed. A device according to claim 1 or 2, wherein said plate (9) has holes (10) enabling it to be screwed to the bonnet of a linear actuation valve (5) whose state is to be sensed. A device according to any one of the preceding claims, wherein said sensors (15, 16) are mechanical sensors requiring contact with said follower stem (6) to indicate arrival of the follower stem at a position corresponding to the desired operating state to be sensed. A device according to one of claims 1 to 3, wherein said sensors (15, 16) are electronic proximity sensors which do not require physical contact for sensing the valve operating state.

Inventors: PIZAO MARCIO REGIS, PIZAO, MARCIO REGIS, Pizao, Márcio Régis
Applicants: PETROLEO BRASILEIRO SA, PETROLEO BRASILEIRO S.A. - PETROBRAS
Application year: 1994
Main classification: F16K37
IPC codes: F16K37